1. Technical Field
The present invention relates to selectively actuable fluid coupling devices and, more particularly, to an improved T-coupling which can be fabricated as a disposable unit and which provides reliable pressure sealing at all interfaces between moving parts.
2. Discussion of the Prior Art
Selectively actuable fluid couplings, and particularly selectively actuable T-couplings, have numerous practical and commercial applications. One such application is surgical aspiration. A prior art fluid coupling device which has been designed for surgical aspiration applications is disclosed in U.S. Pat. No. 4,418,944 (Haines, et al). The disclosure in that patent is expressly incorporated herein in its entirety by this reference for purposes of background information.
The fluid coupling device in the Haines, et al., patent includes a male member which is received in an open-sided generally cylindrical receptacle of a female member. The male member has a transversely extending flow passage adapted to be provided with tubes at either end to establish an aspiration path from the surgical site to an aspirator mechanism. The male member is selectively rotatable in the female member so that a longitudinal bore in the male member, which intersects the transverse flow path, can be selectively aligned with an opening in the receptacle for a bleed supply passage defined in the female member. In order to achieve a tight pressure seal about the bleed passage opening when the bleed supply passage and the bore are aligned, the cylindrical surface of the receptacle, opposite the bleed supply passage opening, is configured with a raised cam and an adjacent detent which cooperate with a cam surface on the male member to force the male and female members together about the bleed passage and bore interface. The absence of cam interaction for other mutual rotational positions of the male and female members minimizes frictional resistance to selective rotation of the male member in use. While this arrangement provides a tight seal and easily controlled rotation between the members, the configured portion of the receptacle surface is subject to wear from repeated use. Thus, while the male member may be disposable, the cam on the permanent female member may eventually wear down and reduce the effectiveness of the seal.
The Haines, et al., patent expresses concern about the occurrence of twisting in the tubes which are attached to the transverse flow passage, particularly as the male member is rotated in the receptacle. In order to prevent such twisting and the resultant working loose of the tubes, Haines, et al., slightly displace the axis of the transverse flow path from the axis of rotation for the male member within the receptacle. This has the effect of imparting somewhat of an arcuate movement (rather than a completely twisting movement) about the flow axis to the attached tubes as the male member rotates in the receptacle. While this improves reliability by reducing the likelihood of the tubes twisting off the male member fittings, the problem is not completely avoided. Specifically, although the transverse flow path axis is not coincident with the rotation axis, the rotation axis still passes through the flow path. A certain degree of twisting is, therefore, still produced, leaving the possibility, although somewhat lessened, that the tubes can twist off their fittings.
For surgical aspiration applications the bleed supply passage provides pressure relief, thereby controlling the degree of aspiration and releasing the aspirator from the surgical site without pulling on tissue which the working tip of the unit may contact. Haines, et al., describe the need for a check valve in the bleed supply passage to control the amount of bleed fluid delivered to the aspirator as a function of pressure in the aspirator line. Haines, et al., note that the use of such check valves in the small diameter surgical tubing is unreliable because the necessarily small valves tend to fail. A solution to this problem is not expressly discussed by Haines, et al., and one is left to assume that the check valve is to remain in the small diameter tube or is disposed in the bleed supply passage upstream of the interface between the bore and the bleed passage opening. In the latter case the check valve becomes part of the permanent or non-disposable equipment and is therefore subject to failure due to extended use.